In fractional-N phase lock loops (PLL's) it is typically required to decrease the charge pump current to narrow the bandwidth. When the charge pump current is reduced in magnitude, it can take time for the PLL to adjust to the new dynamics. If the change is sudden then there will inevitably be some ringing and overshoot in the response that will be slow to die out in narrow-band mode. In the transition from wideband to narrow band modes, the charge pump current is often reduced in steps. The ΣΔ modulator in a fractional-N PLL produces a noise shaped sequence of output codes around the desired fractional value. This translates to sequences of current pulse widths out of the charge pump. If the charge pump changes and the ΣΔ modulator does not know about it, then there will be a disturbance in the PLL that will be slow to settle out, particularly when the bandwidth is reduced.